Film cut-out



H. E. BUTLER Dec. 9, 1930.

FILM CUT-OUT Filed June 12, 1929 I/A/FN/SHEP PA PEA AL UM/NUM Inventor:Henry EESutler; b) HLS Attorney.

Patented Dec. 9, 1930 UNira srra's PATENT GFFICE HENRY E. BUTLER, OFSCOTIA, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COM- PANY, A CORPORATIONOF NEW YORK FILM GUT-OUT Application filed June 12,

The present invention relates to circuit controllers of the type usuallytermed film cutouts and especially to film cutouts of the disc type.Film cutouts of the disc type are used extensively in connection withseries lighting circuits and the manner of their use is well-understoodby those familiar with such lighting circuits. The arrangement employedusually is well-illustrated in the patent to Howell 717,201, datedDecember 30, 1902.

Disk film cutouts in common use comprise two plates of thin metalbetween which is located a suitable insulating material, such as thinpaper, cloth or the like, the plates and insulating material beingunited by an insulating adhesive such as shellac, for example.

In manufacturing film cutouts of this type, it is the practice to coatthe insulating material with an adhesive and then place the coatedmaterial between the two plates, the adhesive serving to stick the partstogether. WVith this arrangement, it has been found that there issometimes considerable variation in the dielectric strength of theinsulation, this being due to the fact that'the coating may be appliedunevenly, or to the fact that in one instance the coating'is thinnerthan in another instance. As a result in some cases, the film willrupture at too low a voltage Whilein other cases it will not ruptureuntil the voltage reaches an undesirably high value. A uniform productwhich will rupture always at the desired voltage is diiiicult toproduce.

The difficulties above referred to are especially noticeable inconnection with the manufacture of disc film cutouts for low voltagecircuits, it being especially difficult to obtain a uniform productwhich will operate reliably on low voltage series circuits.

One object of my present invention is to provide an improvedconstruction of disc film cutout which will enable the cutout to bemanufactured readily and at the same time provide cutouts having uniformbreak-down potentials.

A further object of my invention is to provide a disc type film cutoutwhich can be 1929. Serial No. 370,209.

manufactured with accuracy for any desired breakdown voltage, it beingadapted to be made for low voltage circuits as well as for relativelyhigh voltage circuits.

According to my invention, 1' form my improved film cutout from twometal pieces, separated by a film of insulating material, but instead ofuniting the parts by an adhesive as heretofore, I altogether dispensewith the use of an adhesive and instead unite the two piecesmechanically through the intermediary of an insulating disc, the use ofan insulating disc possessing special advantages as pointed outhereinafter.

In the drawing, Fig. v1 is side elevational View on an enlarged scale ofa cutout embodying my invention, applied to a series incandescent lampholder, said holder being shown in section; Fig. 2 is a centralsectional view of the assembled cutout; and Fig. 3 is an explodedsectional view of the parts which form the cutout. Figs. 2 and 3 aredrawn on a greatly enlarged scale in order better to illustrate theinvention.

, Referring to the drawing, 1 and 2 represent the usual contact arms ofa series incandesc'ant lamp receptacle, such as is in common use forincandescent street-lighting and between the extremities of which thefilm cutout is located. V

Referring to Figs. 2 and'3, 3 and 4; indicate the two metal pieces ofthe cutout separated by the insulating film 5 which may be in the formof lacquer or the like sprayed over one or both of the pieces, or in theform of a separate piece of thin paper, cloth or the like, locatedbetween the two metal pieces The metal piece 4 is of smaller diameterthan the metal piece 3 and the two metal pieces are held in assembledrelation relatively to each other with the insulating film between themby means of an insulating disc 6 formed of material sufficiently stifi"to enable it to hold the parts in their assembledrelation. The metalpiece 4. is provided with a projection 7 at its central portion whichextends through an opening 8 in disc 6 and projects somewhat beyond theconfines of the same. The insulating disc 6 may be fastened to metaldisc 3 in any suitable manner. In the present instance it is shown asbeing fastened to metal disc 3 by means of an inturned flange 9 at theperipheral edge of disc 3. The projection 7 extends beyond the plane ofthe outer surface of the inturned flange 9 so that when the cutout ispositioned between the contact arms 1 and 2, the one contact arm engagesonly the projection 7. Vith this arrangement it will be seen that whenthe cutout is in position, as shown in Fig. 1, disc 3 is in contact withone arm and the projection 7 on disc at is in contact with the otherarm, the two arms being then insulated from each other by the film 5.

The discs 3 and 4 may be formed with advantage from thin aluminum,although any other suitable conducting material may be used. The disc 6may be formed of any suitable insulating material having the desireddegree of stiffness; for example, I may use varnished paper.

In constructing and assembling the cutout I may first form a cup-shapedpiece, as shown at the left-hand side of Fig. The dielectric filmmaterial 5 may be then placed in this cup-shaped piece, the disc 4:placed on top of it, and then insulating disc 6 may be placed over theprojection 7. After the parts are thus assembled the flange of thecupshaped piece may be bent over, as shown in Fig. 2, tightly clampingthe film material 5 and the disc 6 in position, the disc 6 in turnholding the metal disc l. 7 With this arrangement it will be seen thatthe peripheral edges of the metal discs 3 and 4 are well separated fromeach other so that there is no danger of their coming into contactaccidentally. Since the holding disc 6 is formed of insulating materialthere is no possibility of shortcircuiting the cutout when the flange ofthe disc 3 is crimped over, as shown in Fig. 2. This is an importantconsideration as it means that it is unnecessary to take special care inthe manufacture of the cutout.

By my invention, it will be seen that I am enabled to provide a filmcutout comprising only two metal pieces, a dielectric film be tweenthem, and a spacing insulator the use of an adhesive being avoided. Bythis arrangement, I am enabled to select and provide a dielectric filmmaterial which is uniform in dielectric strength and which will punctureat the desired voltage value. As a result, I am enabled to provide filmcutouts which will in all cases be uniform in dielectric strength. Thismeans that I am enabled to provide a uniform product for any desiredvoltage value.

lVhat I claim as new and desire to secure by Letters Patent of theUnited States, is:

1. A film cutout comprising a metal piece, a second metal piece having acentrally disposed struckout portion, an insulating film separating saidpieces, an insulating member which engages the second-named metal piece,

and a flange on the first named metal piece which overlies theinsulating member to hold the metal pieces in fixed assembled relation.

2. A film cutout comprising a metal piece having engaging means, a metalpiece having a centrally disposed struck-out portion, an insulator forseparating said metal pieces, and an insulator having acentrallydisposed perforation adapted to receive the struckout portion of thesecond-named metal piece, said second-named insulator co-operating withthe engaging means of the first-named metal piece and with thesecond-named metal piece for holding said metal pieces in fixedassembled relation.

3. A film cutout comprising two metal discs of different diameters, aninsulating film separating said discs, an insulating disc engaging themetal disc of smaller diameter, and a flange on the metal disc of largerdiameter which clamps said insulating disc to hold the cutout assembled.

In witness whereof, I have hereunto set my hand this 11th day of June,1929.

HENRY E. BUTLER.

CJI

